Small containers are often closed by foil lids adhesively bonded to the peripheral edges of the container openings. The light weight and high flexibility of foil lids makes them very difficult to handle, particularly in high speed processing apparatus. Slight irregularities in the peripheral edges of the container openings make it difficult to obtain a good seal because the foil lids often span such irregularities without being securely bonded to the peripheral edge at the irregularity.